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Cleaning up the throttle body and idle air circuit was a good start.
[Edit: I just read a previous thread of yours. Based on the additional symptoms you mention there, I would agree with the poster that said the O2 sensor is the likely suspect. You can read the rest of this reply if you're interested.]
Just because you clean the idle air control (IAC) valve and it moves freely does not necessarily mean it's okay. It could be sticky and worn out.
You note that the engine idles fine when cold. I can think of two basic things that operationally change when the engine has warmed up: The IAC valve motor contacts are operating in a different zone on the commutator (that area is usually the first to get a wear groove). A problem there will cause a rough idle and/or stalling. The other thing is that the ECU starts to use the input signal from the O2 sensor. A problem there will cause a bad mix and the engine may run rough even at speed. A third suspect would be a failing AMM that doesn't get along with heat. A fourth suspect would be a misadjusted or gummed up throttle position switch (TPS) on the back of the throttle body, although that would not likely allow a smooth cold idle.
When the engine warms and starts to idle rough, tap rapidly and solidly on the side of the IAC with something like a broom handle. If the idle changes or stabilizes that will confirm the IAC. Otherwise I'd focus on diagnosing the O2 sensor (see the FAQ). Do check your air box thermostat. With the engine fully warmed, remove the pre-heat hose from the bottom of the air box and check to see that the flap inside is closed. If it's stuck open then the AMM can get overheated and will (start to) fail. An AMM that is failing, but not dead, can be difficult to diagnose. Doing a "limp home mode" test (see the FAQ and/or do a search) may or may not point the finger at the AMM. While you're there, check the air filter. I wouldn't suspect a plugged fuel filter as that would result in hesitation due to fuel starvation far more evident when accelerating at speed and not likely to cause stalling at idle.
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Dave -940's, prev 740/240/140/120 Never overestimate what little I know.
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